1. Field of the Invention
The present invention relates to laminated nuts for bolts or threaded stud loading and assembly. In particular, the present invention relates to a laminated nut structure having a center threaded tension sleeve.
2. Description of the Prior Art
Conventional hex nut structures create an uneven load concentration when assembled on a mating bolt device. Typically, the load concentration occurs at the lower two to three threads. Conversely, the load concentration on the upper threads is reduced primarily due to dilation of the nut's upper internal diameter as load is placed on the nut, resulting in increased shear forces on the bottom threads. The end result often is loosening of the nut when it is subjected to vibration, leading to ultimate failure of the nut and bolt connection.
In order to overcome the limitations of conventional nut and bolt assemblies, laminated hex nut structures were developed. These structures use a series of laminations with a threaded internal bore to match an associated bolt and a cage holding the parts together. Typically, the nut structures include a bottom plate or washer retained by the cage. Prior art laminated nut structures are disclosed in a series of patents to Reynolds, which are incorporated herein by reference, U.S. Pat. Nos. 4,383,787; 4,900,209; 4,930,962; 4,940,377; 4,984,319; 5,017,079 and 5,049,017. However, a problem with the caged design and threaded laminations is caused by deflection of the laminations under load, this can cause the internal threads to change angle at the point of loading with the bolt. The result can be thread erosion and wear on the bolt or male threads. In addition, reduction of the inside diameter of the laminations contributes to thread erosion. The specific area is the crown of the male thread and root of the female thread. The end result is a compromised nut and bolt assembly, as well as reduced reusability. The conditions related to thread erosion are usually a result of installation over torqueing and the present invention overcomes this problem, as the sleeve type laminated nut of the present invention will support higher loads per thread of engagement.